FTP plugin failed solutions:

Step 1. back up older config file:
cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak

Step 2. vi /etc/ssh/sshd_config
Step 3. set below items or replace it with below content:
UsePAM yes
PermitUserEnvironment yes
Subsystem sftp /usr/libexec/openssh/sftp-server

Step 4.  /sbin/service sshd restart

or execute below shell:
-------------------------------------------------------------------
#!/bin/bash

# Author:       Jerry Cai
# CreateDate:   2012-10-30
# Environment   Linux + Bash

cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak
sed -i '$a \UsePAM yes\nPermitUserEnvironment yes\nSubsystem sftp /usr/libexec/openssh/sftp-server' /etc/ssh/sshd_config
/sbin/service sshd restart
---------------------------------------------------------------------


///////////////////////////////overall result sample ///////////////////////////////////////////
#       $OpenBSD: sshd_config,v 1.69 2004/05/23 23:59:53 dtucker Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options change a
# default value.

Port 333
Protocol 2
SyslogFacility AUTHPRIV
LoginGraceTime 60
PermitRootLogin yes
MaxAuthTries  2
PubkeyAuthentication yes
RhostsRSAAuthentication no
HostbasedAuthentication no
IgnoreUserKnownHosts yes
PasswordAuthentication yes
PermitEmptyPasswords no
X11Forwarding no
PrintMotd yes
PrintLastLog yes
TCPKeepAlive yes
UsePrivilegeSeparation yes
MaxStartups 10
UsePAM yes
PermitUserEnvironment yes
Subsystem sftp /usr/libexec/openssh/sftp-server
